參數(shù)資料
型號(hào): HWD490
廠商: Electronic Theatre Controls, Inc.
元件分類: RS-485
英文描述: Low-Power, Slew-Rate-Limited RS-485/RS-422 Transceivers
中文描述: 低功耗,限擺率限制RS-485/RS-422收發(fā)器
文件頁數(shù): 13/20頁
文件大?。?/td> 502K
代理商: HWD490
Line Length vs. Data Rate
The RS-485/RS-422 standard covers line lengths up to
4000 feet. For line lengths greater than 4000 feet, see
Figure 23.
Figures 19 and 20 show the system differential voltage
for the parts driving 4000 feet of 26AWG twisted-pair
wire at 110kHz into 120
loads.
T ypic al Applic ations
The HWD481, HWD483, HWD485, HWD487–HWD491, and
HWD1487 transceivers are designed for bidirectional data
communications on multipoint bus transmission lines.
Figures 21 and 22 show typical network applications
circuits. These parts can also be used as line
repeaters, with cable lengths longer than 4000 feet, as
shown in Figure 23.
To minimize reflections, the line should be terminated at
both ends in its characteristic impedance, and stub
lengths off the main line should be kept as short as possi-
ble. The slew-rate-limited HWD483 and HWD487–HWD489
are more tolerant of imperfect termination.
Low-Power, S lew-Rate-Limited
RS -485/RS -422 Transc eivers
DI
V
Y
-V
Z
RO
5V
0V
1V
0V
-1V
5V
0V
2
μ
s/div
DI
V
Y
-V
Z
RO
5V
0V
1V
0V
-1V
5V
0V
2
μ
s/div
DI
RO
DE
RE
A
B
RE
RE
RE
RO
RO
RO
DI
DI
DI
DE
DE
DE
D
D
D
R
R
R
B
B
B
A
A
A
120
120
D
R
HWD481
HWD483
HWD485
HWD487
HWD1487
Figure 19. HWD481/HWD485/HWD490/HWD491/HWD1487 System
Differential Voltage at 110kHz Driving 4000ft of Cable
Figure 20. HWD483, HWD487–HWD489 System Differential
Voltage at 110kHz Driving 4000ft of Cable
Figure 21. HWD481/HWD483/HWD485/HWD487/HWD1487 Typical Half-Duplex RS-485 Network
13
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